When building a taller landscape project like a concrete post with the AB Courtyard Collection by Allan Block, added stability may be necessary. Watch detailed information on stacking the blocks, adding a sonotube or changing the foundation if poor soils exist. You can find the entire collection of videos, photos, literature, how-to sheets and instructions all at www.allanblock.com. Allan, Block, blocks, concrete, courtyard, foundation, landscape, post, sonotube, stability, stackable, www.allanblock.com